High frequency amplifier

ABSTRACT

A high frequency amplifier includes a package substrate, an amplifying active device disposed on a top surface of the package substrate, a transmission line connected to the amplifying active device and transmitting a high frequency signal, a surface mounted device (SMD) component shunt-connected at a first end to the transmission line, a SMD component terminal connected to a second end of the SMD component and partially exposed at a back surface of the package substrate, and an external terminal partially exposed at the back surface of the package substrate and connected to a first end of the transmission line, opposite a second end of the transmission line that is connected to the amplifying active device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a high frequency amplifier used incellular phones and S- and C-band wireless communications.

2. Background Art

In cellular phone and S- and C-band wireless communication networks,each coverage area is assigned a particular frequency, or frequencyband, which can be used by communication devices. However, communicationdevice manufacturers desire to avoid manufacture of a different highfrequency amplifier for each such assigned frequency, since thiscomplicates the management of the manufacturing process. Therefore, somehigh frequency amplifiers are designed to be operable in a plurality offrequency bands.

A known such high frequency amplifier will be described with referenceto FIG. 13. In the high frequency amplifier shown in FIG. 13, the signalwhich has been amplified by an amplifying active device 12 is passedthrough a transmission line to the output terminal. Further in this highfrequency amplifier, chip capacitors 21 and 51 are shunt-connected tothe transmission line for matching purposes. A chip inductor and a diode52 are connected to the chip capacitor 51. It should be noted that thediode 52 can be turned on and off by selectively controlling theapplication of the voltage from a terminal 53. That is, the chipcapacitor 51 can be electrically connected to and disconnected fromground by turning on and off the diode 52. This allows the impedance ofthe high frequency amplifier to be set to two values to achieve theoptimum matching conditions in two different frequency bands.

Thus, in some conventional high frequency amplifiers, a chip capacitor,etc. can be connected to and disconnected from ground by use of anactive device such as a diode so that these amplifiers can be operatedin a plurality of frequency bands. Further, high frequency amplifierscapable of amplifying signals in a plurality of frequency bands aredescribed in Japanese Laid-Open Patent Publication Nos. 11-127040(1999), 09-186533 (1997), 10-126173 (1998), and 2008-113202.

As described above, in order to be operated in a plurality of frequencybands, a high frequency amplifier must include an active device and acircuit for controlling it, resulting in an increased parts count. (Theterm “control circuit” is hereinafter used to refer collectively to theactive device and the circuit for controlling it, which device is usedto change the matching conditions of the high frequency amplifier.)

Further, such high frequency amplifiers are also disadvantageous in thatpowering the additional control circuit results in a decrease in theoverall operating efficiency.

SUMMARY OF THE INVENTION

The present invention has been made to solve the above problems. It is,therefore, an object of the present invention to provide a highfrequency amplifier operable in a plurality of frequency bands withoutneed for an additional control circuit for changing the matchingconditions of the amplifier.

According to one aspect of the present invention, a high frequencyamplifier includes a package substrate, an amplifying active devicedisposed on a top surface of the package substrate, a transmission lineconnected to the amplifying active device and transmitting a highfrequency signal, an SMD component shunt-connected at one end to thetransmission line, an SMD component terminal connected to the other endof the SMD component and partially exposed at a back surface of thepackage substrate, and an external terminal partially exposed at theback surface of the package substrate and connected to the end of thetransmission line opposite the end connected to the amplifying activedevice.

According to another aspect of the present invention, a high frequencyamplifier includes a package substrate, an amplifying active devicedisposed on a top surface of the package substrate, a first transmissionline formed on the package substrate so that the first transmission lineis connected in series with the amplifying active device, a secondtransmission line formed on the package substrate so that the secondtransmission line is connected in series with the amplifying activedevice, a first connecting terminal connected to the first transmissionline and partially exposed at a back surface of the package substrate,and a second connecting terminal connected to the second transmissionline and partially exposed at the back surface of the package substrate.

Other and further objects, features and advantages of the invention willappear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a high frequency amplifier of the firstembodiment;

FIG. 2 is a diagram of the high frequency amplifier as viewed from itsback side;

FIG. 3 is an equivalent circuit diagram of the high frequency amplifierof the first embodiment;

FIG. 4 shows a circuit pattern formed on a mounting board;

FIG. 5 shows other circuit pattern formed on a mounting board;

FIG. 6 shows the S21 characteristics (or transmission characteristics)of the high frequency amplifier;

FIG. 7 is a perspective view of a high frequency amplifier including twoSMD components;

FIG. 8 shows an equivalent circuit of the high frequency amplifier shownin FIG. 7;

FIG. 9 shows a first transmission line and a second transmission line;

FIG. 10 shows a circuit pattern formed on a mounting board;

FIG. 11 shows other circuit pattern formed on a mounting board;

FIG. 12 shows an equivalent circuit diagram of the high frequencyamplifier of the second embodiment; and

FIG. 13 shows a prior art amplifier.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A first embodiment of the present invention will be described withreference to FIGS. 1 to 8. It should be noted that throughout thedescription of the first embodiment, certain of the same orcorresponding components are designated by the same reference numeralsand described only once. This also applies to other embodiment of theinvention subsequently described.

FIG. 1 is a perspective view of a high frequency amplifier 10 of thepresent embodiment. In FIG. 1, the dashed lines indicate internalfeatures of the high frequency amplifier 10. The following descriptionof the present embodiment will be directed to the output matching of thehigh frequency amplifier, which matching significantly affects the highfrequency characteristics of the amplifier. The high frequency amplifier10 includes a package substrate 11. The package substrate 11 is, e.g., adouble-sided single-layer resin substrate. An amplifying active device12 is mounted on the top surface of the package substrate 11. Theamplifying active device 12 is connected to a transmission line 13 bywire bonding, etc. The transmission line 13 is a circuit pattern formedon the top surface of the package substrate 11.

The terminal end of the transmission line 13 serves as an output end andis connected to an external output terminal 32. As can be seen from FIG.1, the external output terminal 32 is partially exposed at the backsurface of the package substrate 11. SMD components 21 and 22 areshunt-connected to the portion of the transmission line 13 extendingfrom the amplifying active device 12 to the output end. The SMDcomponents 21 and 22 are chip capacitors or chip inductors. The SMDcomponent 21 is connected at one end to the transmission line 13 and atthe other end to a ground portion. The SMD component 22 is connected atone end to the transmission line 13 and at the other end to an SMDcomponent terminal 33. The SMD component terminal 33 is partiallyexposed at the back surface of the package substrate 11.

FIG. 2 is a diagram of the high frequency amplifier 10 as viewed fromits back side. As can be seen from FIG. 2, both the external outputterminal 32 and the SMD component terminal 33 are exposed at the backsurface of the package substrate 11. The external output terminal 32 andthe SMD component terminal 33 are arranged along an edge of the packagesubstrate 11. Further, a mounting portion 31 is formed on the backsurface of the package substrate 11.

FIG. 3 is an equivalent circuit diagram of the high frequency amplifier10 constructed as described above. Since the SMD component terminal 33is connected or unconnected to ground (as described later), theconnection of the terminal to ground is indicated by a dashed line inFIG. 3.

The high frequency amplifier 10 is mounted on the mounting board of acommunication device, etc. Specifically, the high frequency amplifier 10is mounted on the mounting board so that the back surface of theamplifier is in contact with the top surface of the board which haspatterns formed thereon.

FIGS. 4 and 5 show exemplary patterns formed on the surfaces of mountingboards which are adapted to have the high frequency amplifier 10 mountedthereon. The shaded portions in FIGS. 4 and 5 represent the locationswhere the SMD component terminal 33 is mounted on the mounting boards.The portions indicated by the reference symbol RFoutput in FIGS. 4 and5, on the other hand, represent the locations at which the externaloutput terminal 32 is mounted. Mounting the high frequency amplifier 10on the mounting board shown in FIG. 4 results in the SMD componentterminal 33 being grounded, so that the high frequency amplifier 10amplifies the incoming RF signal at a frequency f1. On the other hand,mounting the high frequency amplifier 10 on the mounting board shown inFIG. 5 results in the SMD component terminal 33 being unconnected toground, so that the high frequency amplifier 10 amplifies the incomingRF signal at a frequency f2 (different from the frequency f1).

FIG. 6 shows the S21 characteristics (or transmission characteristics)of the high frequency amplifier 10 when the amplifier amplifies theincoming signal at around the frequency f1 (i.e., when the amplifier ismounted on the mounting board shown in FIG. 4) and when the amplifieramplifies the incoming signal at around the frequency f2 (i.e., when theamplifier is mounted on the mounting board shown in FIG. 5). Thus, thefrequency at which the high frequency amplifier 10 amplifies theincoming RF signal can be changed by only slightly changing the patternon the surface of the mounting board on which the amplifier is mounted.That is, the use of the high frequency amplifier 10 of the presentembodiment at a plurality of frequencies eliminates the need to usedifferent high frequency amplifiers for these frequencies. That is, thehigh frequency amplifier 10 serves as a general-purpose high frequencyamplifier. Furthermore, the high frequency amplifier 10 of the presentembodiment can be operated in a plurality of frequency bands withoutrequiring an active device and a control circuit therefore to change thematching conditions of the amplifier, that is, without an increase inthe parts count. Further, the elimination of the active device alsoeliminates the need to power the device, preventing a decrease in theoverall operating efficiency of the high frequency amplifier 10.

Although in the present embodiment only one SMD component can beselectively connected and unconnected to ground, it is to be understoodthat the present invention is not limited to this particulararrangement. In other embodiments, for example, a plurality of SMDcomponents may be able to be selectively connected and unconnected toground. A high frequency amplifier including two such SMD componentswill be described with reference to FIGS. 7 and 8. The high frequencyamplifier shown in FIG. 7 differs from the high frequency amplifier 10described above in that it additionally includes an SMD component 23.This high frequency amplifier also includes an SMD component terminal 34connected to the SMD component 23 and exposed at the back surface of thepackage substrate 11. FIG. 8 shows an equivalent circuit of the highfrequency amplifier shown in FIG. 7 when the SMD component terminal 33is connected to ground and the SMD component terminal 34 is unconnectedto ground.

The high frequency amplifier may be designed to amplify the incomingsignal at different frequencies depending on whether the SMD componentterminal 33 or the SMD component terminal 34 is connected to ground onthe mounting board of a communication device. Further, both of the SMDcomponent terminals 33 and 34 may be ungrounded, which allows the highfrequency amplifier to amplify the incoming signal at a differentfrequency than when the SMD component terminal 33 or 34 is grounded.Thus, this high frequency amplifier, which includes a plurality of SMDcomponent terminals each connected to an SMD component, can be operatedin more frequency bands than the high frequency amplifier 10, whichincludes only one SMD component terminal connected to an SMD component.

Further, although the present embodiment has been described inconnection with the output matching of a high frequency amplifier, it isto be understood that the present invention is not limited to outputmatching. For example, the present invention may also be applied toinput matching, etc., with the same effect. That is, in otherembodiments, the terminal end of the transmission line 13 may serve asan input end (or any type of end), and the external output terminal 32may serve as an external input terminal (or any type of externalterminal).

Second Embodiment

A second embodiment of the present invention will be described withreference to FIGS. 9 to 12. A high frequency amplifier of the presentembodiment is constructed such that the frequency at which the amplifieramplifies the incoming RF signal can be changed by changing aninductance component of the amplifier. Referring to FIG. 9, atransmission line 13 includes a first transmission line 15 and a secondtransmission line 16. The inductance of the first transmission line 15differs from that of the second transmission line 16. The firsttransmission line 15 is formed on a package substrate 11 and connectedin series with an amplifying active device 12. The first transmissionline 15 is also connected to a first connecting terminal 36. The firstconnecting terminal 36 is partially exposed at the back surface of thepackage substrate 11.

The second transmission line 16 is formed on the package substrate 11and connected in series with the amplifying active device 12. The secondtransmission line 16 is also connected to a second connecting terminal35. The second connecting terminal 35 is partially exposed at the backsurface of the package substrate 11.

An external output terminal 32 is connected to a third connectingterminal 37 by a conductor formed on the top surface of the packagesubstrate 11. The third connecting terminal 37 is partially exposed atthe back surface of the package substrate 11. That is, the externaloutput terminal 32, the first connecting terminal 36, the secondconnecting terminal 35, and the third connecting terminal 37 are exposedat the back surface of the package substrate 11 of the presentembodiment and spaced from one another. FIG. 12 shows an equivalentcircuit of this high frequency amplifier. Like the high frequencyamplifier of the first embodiment, the high frequency amplifier of thepresent embodiment is mounted on the surface of the mounting board of acommunication device, etc.

FIGS. 10 and 11 illustrate patterns on the surfaces of mounting boardswhich are adapted to have this high frequency amplifier mounted thereon.Mounting the high frequency amplifier on the mounting board shown inFIG. 10 results in the first connecting terminal 36 being connected tothe external output terminal 32 through the third connecting terminal37. That is, the RF signal passes through the first transmission line15. It will be noted that the shaded portion in FIG. 10 represents thelocation where the first connecting terminal 36 is in contact with thepattern.

On the other hand, mounting the high frequency amplifier on the mountingboard shown in FIG. 11 results in the second connecting terminal 35being connected to the external output terminal 32 through the thirdconnecting terminal 37. That is, the RF signal passes through the secondtransmission line 16. It will be noted that the shaded portion in FIG.11 represents the location where the second connecting terminal 35 is incontact with the pattern. Thus, the RF signal passes through the firsttransmission line 15 or the second transmission line 16 depending onwhether the high frequency amplifier is mounted on the mounting boardshown in FIG. 10 or 11, since these mounting boards have suitabledifferent patterns formed thereon. This allows for the same effect asdescribed in connection with the first embodiment.

Further, since in the high frequency amplifier of the present embodimentthe first connecting terminal 36 and the second connecting terminal 35are disposed adjacent each other, it is easy to design the connectingwiring on the mounting boards on which the amplifier is to be mounted.

The present invention enables the manufacture of a high frequencyamplifier which is simple in construction yet can be operated in aplurality of frequency bands.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

The entire disclosure of a Japanese Patent Application No. 2010-004272,filed on Jan. 12, 2010 including specification, claims, drawings andsummary, on which the Convention priority of the present application isbased, are incorporated herein by reference in its entirety.

1-3. (canceled)
 4. high frequency amplifier comprising: a packagesubstrate; an amplifying active device disposed on a top surface of saidpackage substrate; a first transmission line located on said packagesubstrate so that said first transmission line is connected in serieswith said amplifying active device; a second transmission line locatedon said package substrate so that said second transmission line isconnected in series to said amplifying active device; a first connectingterminal connected to said first transmission line and partially exposedat a back surface of said package substrate; and a second connectingterminal connected to said second transmission line and partiallyexposed at said back surface of said package substrate.
 5. The highfrequency amplifier according to claim 4, wherein said first and secondconnecting terminals are disposed adjacent each other.